Salmon in aquaculture pens have limited opportunity to express natural behaviours. Environmental enrichment can improve welfare by providing complexity and reducing the monotony of intensive rearing conditions.
Salmon welfare in intensive aquaculture suffers partly from the monotony of the rearing environment. Wild salmon occupy structurally complex habitats — riverbeds with boulders, undercut banks, and varied current — that provide both physical stimulation and opportunities for thermoregulation and refuge from predators and competitors. Circular sea cages provide none of this complexity: fish swim in homogeneous water columns with no substrate, no cover, and no flow variation. Research into enrichment for farmed salmon is at an early stage but promising: submerged cover structures increase habitat use diversity, and flow variation encourages the natural rheotaxis (facing into current) that salmon are evolved to perform. Enrichment does not resolve all salmon welfare challenges but represents a meaningful improvement within the constraints of current production systems.